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<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>

<style>
* { padding: 0; margin: 0; }
li { list-style: none; }

ul { width: 400px; height: 30px; position: relative; margin: 100px auto 0; }
li { float: left; width: 98px; height: 28px; line-height: 28px; border: 1px solid #ccc; text-align: center; z-index: 2; position: relative; cursor: pointer; }
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<script type="text/javascript">
window.onload=function(){
	var oUl=document.getElementById('ul1');
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</head>

<body>

<ul id="ul1">
	<li>首页</li>
	<li>关于我们</li>
	<li>产品</li>
	<li>联系方式</li>
    <li class="bg"></li>
</ul>

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